Heat pipe

ABSTRACT

A heat pipe includes a casing having an inner wall. A plurality of protrusions are radially formed on the inner wall of the casing. The plurality of protrusions are spaced from each other and extend longitudinally from one end of the casing to the other end of the casing. A main groove is defined between every two adjacent protrusions. The protrusions each define a plurality of first auxiliary grooves and a plurality of second auxiliary grooves being alternatively arranged with respect to each other along a longitudinal direction of the casing. The first auxiliary and the second auxiliary grooves each communicate two adjacent main grooves. The first auxiliary grooves each are inclined at an angle with respect to a longitudinal axis of the casing, and the second auxiliary grooves each are inclined at another different angle with respect to the longitudinal axis of the casing.

BACKGROUND

1. Technical Field

The present invention relates generally to a heat pipe, and particularlyto a grooved heat pipe.

2. Description of Related Art

Heat pipes have excellent heat transfer performance due to their lowthermal resistance, and are therefore an effective means for transfer ordissipation of heat from heat sources. Currently, heat pipes are widelyused for removing heat from heat-generating components such as centralprocessing units (CPUs) of computers. A heat pipe is usually a vacuumcasing containing therein a working medium, which is employed to carry,under phase transitions between liquid state and vapor state, thermalenergy from one section of the heat pipe (typically referring to as the“evaporator section”) to another section thereof (typically referring toas the “condenser section”). Preferably, a wick structure is providedinside the heat pipe, lining an inner wall of the casing, for drawingthe working medium back to the evaporator section after it is condensedat the condenser section. The wick structure currently available for theheat pipe includes fine grooves integrally formed at the inner wall ofthe casing.

In operation, the evaporator section of the heat pipe is maintained inthermal contact with a heat-generating component. The working mediumcontained at the evaporator section absorbs heat generated by theheat-generating component and then turns into vapor. Due to thedifference of vapor pressure between the two sections of the heat pipe,the generated vapor moves and thus carries the heat towards thecondenser section where the vapor is condensed into condensate afterreleasing the heat into ambient environment by, for example, finsthermally contacting the condenser section. Due to the difference incapillary pressure which develops in the wick structure between the twosections, the condensate is then brought back by the wick structure tothe evaporator section where it is again available for evaporation.

In order to draw the condensate back timely, the wick structure providedin the heat pipe is expected to provide a high capillary force andmeanwhile generate a low flow resistance for the condensate. If thecondensate is not quickly brought back from the condenser section, theheat pipe will suffer a dry-out problem at the evaporator section.

Therefore, it is desirable to provide a heat pipe with improved heattransfer capability.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present embodiments can be better understood withreference to the following drawings. The components in the drawings arenot necessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the present embodiments.Moreover, in the drawings, like reference numerals designatecorresponding parts throughout the several views.

FIG. 1 is a partially isometric view of a heat pipe in accordance withan exemplary embodiment of the present invention.

FIG. 2 is a longitudinally cross-sectional view of the heat pipe of FIG.1, taken along line II-II thereof.

FIG. 3 is a stretch-out view of the heat pipe of FIG. 1.

FIG. 4 is a partially cross-sectional view of the heat pipe, taken alongline IV-IV of FIG. 3.

DETAILED DESCRIPTION

Referring to FIGS. 1-2, a heat pipe 10 includes an elongated, round andtubular casing 11 containing a working fluid (not shown) therein,wherein only a section of the casing 11 is shown in the figures forillustrating the principle of the heat pipe 10.

The casing 11 is made of high thermally conductive material such ascopper or aluminum. An inner wall 110 of the casing 11 defines a vaporchannel 15 extending from a front end towards a rear end of the casing11. A plurality of elongated protrusions 13 are radially and inwardlyformed on the inner wall 110 of the casing 11 and circumferentially andevenly spaced from each other. The plurality of protrusions 13 eachextend longitudinally from the front end towards the rear end of thecasing 11. An elongated main groove 12 is defined between every twoadjacent protrusions 13.

A plurality of first annular auxiliary channels 14 and a plurality ofsecond annular auxiliary channels 17 are circumferentially defined inthe plurality of protrusions 13. The plurality of first annularauxiliary channels 14 and the plurality of second annular auxiliarychannels 17 are alternately arranged with respect to each other along alongitudinal direction of the casing 11, whereby each of the protrusions13 is longitudinally divided into a plurality of sections.

Each of the first annular auxiliary channels 14 includes a plurality offirst auxiliary grooves 18 being circumferentially defined in theplurality of protrusions 13. Each of the second annular auxiliarychannels 17 includes a plurality of second auxiliary grooves 19 beingcircumferentially defined in the plurality of protrusions 13. The firstauxiliary grooves 18 and the second auxiliary grooves 19 in eachprotrusion 13 are alternately arranged with respect to each other alongthe longitudinal direction of the casing 11 and evenly spaced from eachother.

Each of the first auxiliary grooves 18 is inclined at an angle a withrespect to a longitudinal axis of the casing 11, and each of the secondauxiliary grooves 19 is inclined at another different angle β withrespect to the longitudinal axis of the casing 11. In the illustratedembodiment, the angle α of the first auxiliary groove 18 is smaller than90 degrees, and the another angle β of the second auxiliary groove 19 islarger than 90 degrees. The angle α of the first auxiliary groove 18 iscomplementary to the another angle β of the second auxiliary groove 19(i.e., α plus β equaling 180 degrees). Preferably, the first auxiliarygroove 18 and the second auxiliary groove 19 communicate with a maingroove 12 are inclined along the longitudinal direction of the heat pipe10 from an evaporator section (not shown) to a condenser section (notshown) thereof to two different sides of the main groove 12. Theevaporator section is located at the front end of the casing 11, whilethe condenser section is located at the rear end of the casing 11. Thefirst auxiliary grooves 18 and the second auxiliary grooves 19 areextended toward substantially opposite directions, whereas as shown inFIG. 3, the first auxiliary grooves 18 extend upwardly rightwards andthe second auxiliary grooves 19 extend upwardly leftwards.

The first auxiliary groove 18 has a depth equal to the second auxiliarygroove 19. Each of the first auxiliary groove 18 and the secondauxiliary groove 19 has a depth greater than the main groove 12, asshown in FIG. 4. In alternative embodiments, each of the first auxiliarygroove 18 and the second auxiliary groove 19 has a depth smaller thanthe main groove 12 or equal to the main groove 12.

The working fluid is saturated in the main grooves 12, the firstauxiliary grooves 18 and the second auxiliary grooves 19. The workingfluid is usually selected from a liquid such as water, methanol, oralcohol, which has a low boiling point. Thus, the working fluid caneasily evaporate to vapor when it receives heat at the evaporatorsection of the heat pipe 10. The generated vapor moves via the vaporchannel 15 towards the condenser section of the heat pipe 10. After thevapor releases the heat carried thereby and is condensed into the liquidin the condenser section, the liquid is brought back by a capillaryaction of the main grooves 12, the first auxiliary grooves 18 and thesecond auxiliary grooves 19 to the evaporator section of the heat pipe10 for being available again for evaporation.

The first auxiliary grooves 18 and the second auxiliary grooves 19defined in the protrusions 13 increase a receiving room for containingthe working fluid therein, without increasing a size of the heat pipe10. Meanwhile, the first auxiliary grooves 18 and the second auxiliarygrooves 19 communicate a main groove 12 with an adjacent main groove 12,whereby the working fluid can flow between the two adjacent main grooves12 via the first auxiliary grooves 18 and the second auxiliary grooves19. Moreover, the first auxiliary grooves 18 and the second auxiliarygrooves 19 function as supplemental wick structures to improve thecapillary action of the heat pipe 10.

It is believed that the present embodiments and their advantages will beunderstood from the foregoing description, and it will be apparent thatvarious changes may be made thereto without departing from the spiritand scope of the invention or sacrificing all of its materialadvantages, the examples hereinbefore described merely being preferredor exemplary embodiments of the invention.

1. A heat pipe comprising: a casing having an inner wall; a plurality ofprotrusions radially formed on the inner wall of the casing, theplurality of protrusions being spaced from each other and extendinglongitudinally from one end of the casing to another end of the casing,a main groove being defined between every two adjacent protrusions, theprotrusions each defining a plurality of first auxiliary grooves and aplurality of second auxiliary grooves therein, the first auxiliarygrooves and the second auxiliary grooves in each of the protrusionsbeing alternately arranged with respect to each other along alongitudinal direction of the casing, each of the first auxiliarygrooves and the second auxiliary grooves communicating a main groovewith an adjacent main groove, the first auxiliary grooves each beinginclined at an angle with respect to a longitudinal axis of the casing,the second auxiliary grooves each being inclined at another differentangle with respect to the longitudinal axis of the casing.
 2. The heatpipe as claimed in claim 1, wherein the first auxiliary grooves and thesecond auxiliary grooves are inclinedly extended to two oppositelydifferent directions along the longitudinal axis of the casing from theone end of the casing to the another end of the casing.
 3. The heat pipeas claimed in claim 1, wherein the angle of the first auxiliary groovesis smaller than 90 degrees, and the another different angle of thesecond auxiliary grooves is larger than 90 degrees.
 4. The heat pipe asclaimed in claim 1, wherein the angle of the first auxiliary grooves iscomplementary to the another different angle of the second auxiliarygrooves.
 5. The heat pipe as claimed in claim 1, wherein each of thefirst auxiliary grooves and the second auxiliary grooves has a greaterdepth than the main groove.
 6. A heat pipe comprising: a casing havingan inner wall; a plurality of protrusions formed on the inner wall ofthe casing, the plurality of protrusions being spaced from each otherand extending longitudinally through two opposite ends of the casing, amain groove being defined between two adjacent protrusions, a pluralityof first annular auxiliary channels and a plurality of second annularauxiliary channels being defined in the plurality of protrusions, thefirst annular auxiliary channels and the second annular auxiliarychannels being alternately arranged with respect to each other along alongitudinal direction of the casing, each of the first annularauxiliary channels comprising a plurality of first auxiliary groovesbeing circumferentially defined in the plurality of protrusions, each ofthe second annular auxiliary channels comprising a plurality of secondauxiliary grooves being circumferentially defined in the plurality ofprotrusions, the first auxiliary grooves each being inclined at an anglewith respect to a longitudinal axis of the casing, the second auxiliarygrooves each being inclined at another different angle with respect tothe longitudinal axis of the casing.
 7. The heat pipe as claimed inclaim 6, wherein the first auxiliary grooves and the second auxiliarygrooves are inclinedly extended to two oppositely different directionsalong the longitudinal direction of the casing.
 8. The heat pipe asclaimed in claim 6, wherein the angle of the first auxiliary grooves issmaller than 90 degrees, the another different angle of the secondauxiliary grooves is larger than 90 degrees.
 9. The heat pipe as claimedin claim 6, wherein the angle of the first auxiliary grooves iscomplementary to the another different angle of the second auxiliarygrooves.
 10. The heat pipe as claimed in claim 6, wherein each of thefirst auxiliary and second auxiliary grooves has a greater depth thanthe main groove.